In the related art, although not a molding die for a composite material, assembly jigs for structural components made from composite materials are known (for example, refer to Patent Document 1). The assembly jig for structural components made from composite materials is provided with a jig structure, a pilot plate provided on an top surface side of the jig structure, a slide mechanism provided between the jig structure and the pilot plate, and a fitting and a locator provided between the pilot plate and the structural component made from a composite material. The locator is a member for adjusting the position at which a structural component made from a composite material is horizontally supported in the up and down direction.